1. Field of the Invention
The invention relates to guided missiles, and concerns more particularly a lateral gas jet piloting device for such missiles.
2. Description of the Prior Art
The maneuvering ability of offensive targets is constantly being improved, such that the terminal trajectory error, or passing distance, of the missiles increases accordingly. In a conventional guided missile which uses a piloting device of an aerodynamic type requiring an incidence measurement for modifying its flight path, the time consant related to the aerodynamic response is of the order of a few tenths of a second. In comparison, a lateral gas jet piloting device which creates a system of forces applied to the center of gravity of the missile so as to ensure the direct movement of the center of gravity with respect to its path, time constants less than a tenth of a second are possible.
It is known that the path or trajectory of a missile may be modified by ejection of a material jet whose flowrate and direction are varied so as to create a given thrust force. This thrust force may be obtained from numerous energy sources, such a liquid propergols. Whereas lateral gas jet piloting devices using liquid propergol energy sources provide flexible operation because these energy sources may be activated or de-activated intermittently on demand, they present the drawback of excessive complexity, a certain temperature sensitivity and especially of being difficult to store. Therefore, in the piloting device considered here, the energy souce is formed by solid propergol whose combustion provides a continuous gas flow. One difficulty inherent in the use of a solid propergol follows from the fact that once the combusion has been completely initiated the combusion pressure must be maintained within limits which vary little ; a second difficulty results from the fact that, since the flow rate of the gas flow is continous the resultant of the thrust forces applied to the missile must be zero in the absence of piloting order.
A lateral gas jet piloting device comprises at least one pair of diametrically opposite nozzles, but more generally two pairs of nozzles orientated in two mutually orthogonal piloting planes, these nozzles being fed from an energy source supplying a gas flow with substantially constant flowrate, and routing means are included for modifying the differential gas flow between the nozzles so as to create a resultant thrust force of given magnitude and direction.
From European patent application No. 82 400 634 O filed in the name of the present Applicant, a lateral gas jet piloting device is known which attains the abovementioned objectives. This device comprises two pairs of nozzles, each of these pairs of nozzles is oriented in the piloting planes of the missile. The differential gas flow in each of the pairs of nozzles is controlled by a switch formed of two rotatably mounted vanes placed in the gas ducts of the nozzles, these vanes are mechanically coupled to a pneumatic double-acting cylinder and allow one and the other of the nozzles to be cleared alternately.
This known piloting device, although it may operate satisfactorily, present limitations when it is desired to construct a piloting device taking up reduced space and having a short response time, while striving for a manufacturing cost adapted to the cost of the missile.